Everyone who loves a good romance has seen The Notebook. And if you haven't seen it, you've read it. The two main characters, Noah and Allie, are played by Ryan Gosling and Rachel McAdams respectively. When you think of The Notebook, you think of those two stars. But what if things had gone differently back in the early 2000s, when the movie was cast? What if Rachel McAdams hadn't been Allie... but instead, Jessica Simpson had? It turns out, there's a sizable reason as to why Jessica turned the role down.